1. Technical Field
The present invention relates generally to the field of semiconductor manufacturing and, more specifically, to a method for forming unlinked features.
2. Background Art
The need to remain cost and performance competitive in the production of semiconductor devices has caused continually increasing device density in integrated circuits. To facilitate the increase in device density, new technologies are constantly needed to allow the feature size of these semiconductor devices to be reduced.
Many of the current technologies used to reduce the feature size inherently result in the creation of loops rather than unlinked, discrete feature lines. For example, image enhancing techniques such as phase shifting and sidewall image transfer create loops rather than discrete lines. To use these techniques to create unlinked features, further processing is required to segment the loops. This is typically done with an additional mask level used to pattern a trim shape over sections of the loop. A develop or etch process is then used to removed the undesired portions. These further processing steps required to segment the linked features introduces undesirable process complexity that increases the probability of defects in the final device.
Previously, a new frequency doubling hybrid photoresist was developed to extend photolithography to a smaller feature size. The hybrid resist uses the edges of the mask shapes to define the feature spaces in the resist. However, because the edge of the mask shape continues around the entire perimeter of the shape, these edge defined spaces are all linked together. Thus, like other image enhancing techniques, features created using hybrid resist are "linked" together. While this linking is acceptable in some situations, such as in the formation of shallow trench isolations, the linking can be unacceptable in other situations where the linking can cause unwanted shorting. Again, to overcome this, additional processing steps are required to trim the linked features.
The use of these additional processing steps to trim linked features in traditional photolithography or when using hybrid resist is undesirable for several reasons. First, the additional processing complexity increases the time and number of steps needed to form features. Second, the use of the additional mask levels increase the probability of overlay errors in the fabrication process.
For these reasons, what is needed is a method for forming unlinked features ing image enhancement techniques that do not unreasonably increase process complexity.